© 2014 HDR, Inc., all rights reserved.

Utilizing Two Dimensional Hydraulic Modeling on West Cathedral Channel

Deborah de Chambeau, P.E., CFM Yunjing Zhang, P.E., CFM Mitchell Blum, P.E., CFM Mark Seits, P.E., CFM

Project Overview Project Location Project Purpose HEC-RAS 2D Capability HEC-RAS 2D Modeling o Geometry o Unsteady Flow o RAS Mapper o Model Results

Project Location

Study Area - Purpose

Study area Eagle Canyon Dam o Recently constructed upstream of the study area o CLOMR has been submitted in 2014

Cove Development West Cathedral Channel North Cathedral Channel, East

Cathedral Channel Levees

Project Purpose

Eagle Canyon Dam o Recently constructed upstream of the study area o Commercial Area to be remove from floodplain due

to North Cathedral Channel o Depth and duration of the flooding

Floodplain due to West Cathedral Channel o Zone AE within channel banks o Zone A outside of channel banks

Project Description

West Berm o Not Certified Levee

East Levee Concrete Channel Downstream of Bridge 111 Model with and without Berm conditions

West Berm

Concrete Channel

Levee West Cathedral Channel

Results – 1D

Why 2D modeling

HEC-RAS 1 Dimensional Model Limitations Overland Flow Complex Hydrodynamic Flow Flow Breakout Flow Depth Model with and without Berm conditions

HEC-RAS 2 D Model Capabilities HEC-RAS 5.0 Beta Version o 2D Capability

HEC-RAS 2D Modeling Capabilities o Can perform 1D, 2D and combined 1D and 2D

modeling o Solve Full Saint-Venant or Diffusion Wave

Equation o Unstructured or structured computational meshes o Detailed Hydraulic Table properties for 2D

computational cells and cell faces o Detailed flood mapping and flood animations

Current HEC-RAS 2 D Model Limitations Can’t perform sediment transport erosion Can’t perform water quality modeling Can’t connect pump stations to 2D flow area

cells Can’t use the HEC-RAS bridge modeling

capacity

Geometry Terrain 2D Flow Area

o 3 – 2D areas o Mesh – regular and Irregular size o Cell size 10x10 o Breaklines

Geometry (Cont’d)

Boundary Condition o 2D – Area BC line o 2D - Normal Depth o 2D - Flow Hydrograph o 1D – Flow Hydrograph (Upstream) o 1D - Stage Hydrograph (Downstream)

Geometry (Cont’d)

1D - Channel o Bridge

1D/2D Connection o Lateral Structures

Land Cover to Manning’s n

1D area – Manning’s n o Channel, overbanks

2D Flow Area o Land Cover Name and Base Manning’s

n numbers were assigned o Associated layer

Unsteady Flow Analysis

Geometry o With West Berm o Without West Berm

Unsteady Flow o 100 year 3 hour - controls o 100 year 6 hour o 100 year 24 hour o 10 year 3 hour o 50 year 3 hour

RAS Mapper

Results (without Berm) Results (with Berm)

100-year 3 hour

Results (Max Depth, Velocity)

Results (Water Surface El.)

Results – Animation